My '05 RX330 has a problem with the heater. In MA, about 50-58oF and trying to put the heater at 80-HIGH either on auto or A/C. Sometimes it blows hot air and then switches to cold or gets really hot, or just runs cold for a bit. Checked coolant, it was low so filled it this evening. Didn't seem to make a difference. Had tuneup 15k miles ago so coolant has not been filled to my knowledge in a year.....

Seems 'intuitively' like some sensor is off, the one which measures the temperature in the car and filters mixture of hot and cold to achieve the selected manual temperature. But when I manually select to "HIGH" I thought this should always blow hot air no matter the temperature in the car.... ? [In the past in summer if I wanted a bit of heat in the car I would have to put it on HIGH to get some warm air, as obviously the sensor thought the car was 80+. E.g., HIGH setting always produced heat.]

If after all this you have no luck. And want to start a new topic. State which type of car and equipment you have installed. For example the year. Is it a 330 or 350. FWD or AWD. Is it a Lexus that was sold in the states or overseas. Mark Levinson or Premium Stereo. Navigation. Rear Entertainment. Does the system work and your only getting a warning. Things like that.

On your Air Conditioning system. There has been numerous postings about heater and A/C air flow and temperature problems. A 1 minute search of this web page. Showed these postings.

Again. When your looking for help. Look in all of the Lexus models. They all use the same systems.

Not sure what are 'cels'; sorry. On cold setting it runs cold. Problem is getting any heat. Heat is very inconsistent. Should be giving me heat (based on past performance) from 80+ manual setting but certainly when manual HIGH is set. Sometimes it does, sometimes it doesn't... !

If after all this you have no luck. And want to start a new topic. State which type of car and equipment you have installed. For example the year. Is it a 330 or 350. FWD or AWD. Is it a Lexus that was sold in the states or overseas. Mark Levinson or Premium Stereo. Navigation. Rear Entertainment. Does the system work and your only getting a warning. Things like that.

On your Air Conditioning system. There has been numerous postings about heater and A/C air flow and temperature problems. A 1 minute search of this web page. Showed these postings.

Again. When your looking for help. Look in all of the Lexus models. They all use the same systems.

My '05 RX330 has a problem with the heater. In MA, about 50-58oF and trying to put the heater at 80-HIGH either on auto or A/C. Sometimes it blows hot air and then switches to cold or gets really hot, or just runs cold for a bit. Checked coolant, it was low so filled it this evening. Didn't seem to make a difference. Had tuneup 15k miles ago so coolant has not been filled to my knowledge in a year.....

Seems 'intuitively' like some sensor is off, the one which measures the temperature in the car and filters mixture of hot and cold to achieve the selected manual temperature. But when I manually select to "HIGH" I thought this should always blow hot air no matter the temperature in the car.... ? [In the past in summer if I wanted a bit of heat in the car I would have to put it on HIGH to get some warm air, as obviously the sensor thought the car was 80+. E.g., HIGH setting always produced heat.]

Suggestions? Thanks.

Was it consistent with delivering cool air in summer (with AC off)?
My RX330 was not consistent and after a stop gave me warm air instead of cool (from outside). If AC was on, it always made it cold, but without AC - sometimes warm.

Was it consistent with delivering cool air in summer (with AC off)?
My RX330 was not consistent and after a stop gave me warm air instead of cool (from outside). If AC was on, it always made it cold, but without AC - sometimes warm.

Yes, I believe it did deliver cool air in summer (manual had been set to 75 when it was running).. with the AC off. Gusar - what ended up being the problem for you, and how was it resolved? Thanks.

Yes, I believe it did deliver cool air in summer (manual had been set to 75 when it was running).. with the AC off. Gusar - what ended up being the problem for you, and how was it resolved? Thanks.

Actually, my problem was not resolved. Just fall came
I think in my case something is not stable in the control block - vent door sometimes stop moving. Not often though. Now it works (heats).
Basically there are three areas for your problem to be potentially responsible:
1. Control block and temp. sensor
2. Servo motors/doors' mechanics/contacts
3. Clogged heater radiator(s).

I would bet on #1 or 2. If you can get access and see doors moving or stuck (when changing temp. setting), you may be closer to resolving the problem.

Gusar- thanks. I plan to take it to a local auto repair shop that deals with a/c issues rather than to the dealer, and will bring your list; make sense. Fan power is fine from what I can sense. Things improved a bit after I got the coolant back to level, but definitely a problem with the a/c.

They are located under the dash in the center console. Over on the passenger side.

Here is a picture of one taken apart.

Thanks, MC5Wes.. Took the car to a mechanic today who looked at it briefly; he thinks it's either the thermostat, water pump (replaced 15k miles ago with timing belt), or a blocked heater core. Called another mechanic who was recommended and he said 9 times out of 10, flushing the heater core takes care of the problem. Big bucks if the heater core is leaking. I too thought it might be a servo; probably the cooling servo. What symptoms did you have that led you to the servo motors?

Will take it to the 2nd mechanic in a few days and get an assessment. From what I've read on this forum, repair/replacing the heater core is a huge job, so hoping it isn't that....